Unit Name: Dunvegan Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Cenomanian (99.6 - 93.6 ma)
Age Justification: The Dunvegan carries a rich shallow water fauna in the type area and in the Kakwa River area. It carries an extensive dicotyledon flora in northeastern British Columbia. Oysters, mussels, unionids and Inoceramus are common in Alberta, with I. rutherfordi indicating correlation with the Belle Fourche Shale of Wyoming. An arenaceous assemblage of Foraminifera dominated by Trochammina is found in brackish water tongues. The fossils indicate an Upper Cenomanian Age. The flora carries Platanus, Pseudocycas unjiga and numerous conifers and cycads, and ferns.
Province/Territory: Alberta; British Columbia
Originator: Dawson, 1881.
Type Locality:
Near Dunvegan, on the Peace River, northwestern Alberta.
Distribution:
Thickness is around 160 to 180 m (525 to 590 ft) in the Peace River area of Alberta, thinning to the south and east and disappearing; it is over 380 m (1,246 ft) in the foothills of the Pine River. The Dunvegan extends from Fort Nelson and the Liard River over the entire Peace River area and as far south as Wildhay River in the foothills.
Lithology:
Consists of marine, nonmarine and deltaic sandstone, light grey to yellowish buff in the type area. Beds may be massive, with cross-bedding. Thin beds of shale, shelly limestone and coal are present. The Dunvegan is dominantly marine in the area east of Dunvegan, but completely continental in northeastern British Columbia, where thick arkosic and conglomeratic beds are common. South of the Wapiti River in the foothills, and across the Grande Prairie area the sands are brackish water to marine and usually porous.
Relationship:
The Dunvegan Formation is overlain conformably by the Kaskapau Formation in the Peace River area, except for an apparent hiatus near Watino, Alberta where the Dunveganoceras Zone seems to be missing. The contact is usually transitional, and where the basal unit of the Kaskapau becomes overly sandy the term Sakunka Member of the Dumvegan was suggested by Spieker (1921) for such beds in the Pine River area of British Columbia. The Dunvegan is underlain conformably and transitionally by shales of the Fort St. John Group, which are referred to as Sully and Cruiser formations in northeastern British Columbia and as the Shaftesbury Formation in the Peace River plains of Alberta. The Dunvegan grades laterally to the east into the marine Labiche Formation and to the south into the middle part of the Sunkay Member of the Blackstone Formation. To the southeast in the plains the equivalent beds would be found in the lower Colorado Group between the Second White Specks and the Fish scale marker bed. It coarsens northward to become the continental Fort Nelson conglomerate in northeastern British Columbia, which Stott (1968) included in the Dunvegan.
Other Citations:
Dawson, 1881; Gleddie, 1949; McLearn, 1945; Spieker, 1921; Stelck, 1962; Stott, 1960, 1968.
References:
Dawson, G.M., 1881. Report on the exploration from Port Simpson on the Pacific Coast to Edmonton on the Saskatchewan River, Embracing a portion of the northern part of British Columbia and the Peace River country, with Maps 150 and 152; Geological Survey of Canada, Report of Progress 1879-1880, Part B, p. 1-77.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: C.R. Stelck
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 May 2008